There are three types of insurance involved. Your homeowners/personal liability insurance is first, for you. Most people have something like $300,000/100,000.
Secondary insurance is through your AMA membership- up to $2.5 million additional.
Thirdly, any sanctioned contest has primary coverage for the site owner, $2.5million, through the sanction. For non-sanctioned club events most clubs get similar primary coverage for the site owner through the club registration.
You can look up information from the insurance program in the members only tab on the AMA website modelaircraft.org.
By far and away the largest cost to AMA is the insurance, nearly $1.8 million in premiums, costs, lawyers, and pay outs. There is some info on payouts which for the most part seem to run up to $25,000 or so in medical costs and other payouts for other damages in lesser amounts.
If something does happen, call 911, take names and info, and get in touch with the AMA as soon as possible. As the airlines have found, fast, helpful response to accidents pays dividends.